Communication in an enterprise is often cumbersome, because users typically have desk phones and mobile phone terminals with multiple phone numbers and multiple messaging systems. This situation arises in most enterprises, which generally do not have mobile network coverage in their offices. Consequently, enterprise users often use two different phones: one for outside the office and one for in the office. Enterprise users therefore have to deal with multiple phone numbers and devices depending on location, and corresponding voicemail and messaging systems associated with the various devices and systems. As workers and other organizational members become increasingly mobile, enterprises need solutions to make communications more effective, reliable and mobile.
Some enterprises have attempted to use a voice over wireless local area network (VoWLAN) to provide some mobile communication within the enterprise facilities. However, most VoWLAN implementations provide a relatively low degree of reliability, to which most users are not accustomed relative to wired telephone systems (e.g., 99.999% reliability for voice calls). In the past, for an existing VoWLAN to have a better degree of reliability, the VoWLAN was very dense and thoroughly tested, which made the VoWLAN more costly to build. Also, existing VoWLANs typically require many access points to provide mobility within an enterprise, because of the relatively limited range of WLAN communications. Further, the bandwidth of a VoWLAN is subject to variable loads from computing devices and other mobile terminals. For example, if a computing device transferred a relatively large file during a VoWLAN call, a delay in the voice call could be caused.
Currently, there is are relatively meager fail-over mechanisms for VoWLAN networks to switch to an alternate network if the wireless local area network (WLAN) becomes unsuitable for voice communication with a mobile terminal. Moreover, current VoWLAN and voice over Internet protocol (VoIP) solutions have difficulty with live session handovers between mobile networks and WLANs. Mobile terminals typically have one type of wireless communication interface, or are restricted to completing a session on the network that it was initiated. Consequently, enterprise members typically have separate wired and wireless phones with associated voicemail systems to make the enterprise members more reachable.